Chiral 6,6′-disilylated binaphthoxyphosphazene copolymers carrying diphenyl-phosphine-phenoxy groups inside wide chiral pockets

The reaction of the chiral phosphazene copolymer {[NP(O2C20H10Br2)](0.8)[NP(OC6H4PPh2)(2)](0.2)}(n) (I) [(O2C20H10Br2)=R-6,6'-dibromo-2,2-dioxy-1,1-binaphthyl] with (BuLi)-Bu-t in THF gave the intermediate {[NP(O2C20H10Li2)](0.8)[NP(OC6H4PPh2)(2)](0.2)}n (II) that was treated with the chlorosilanes SiR1R2R3Cl to give the new polyphosphazenes {[NP(O2C20H10{SiR1R2R3}(2))](0.8)[NP(OC6H4PPh2)(2)](0.2)}(n) [R1R2R3=Me-3 (III), R1R2R3=Me2Ph (IV), R1R2R3=MePh2 (V), R1R2R3=Ph-3 (VI)], in which the phosphine ligands are located inside sterically demanding chiral pockets. The almost inevitable presence of oxidized OC6H4P(O)Ph-2 groups in those polymers was successfully resolved by a quantitative removal of the oxygen by the SiHCl3/PPh3 method that was adapted to high M-w polymers. The new polyphosphazenes had M-w of the order of 10(6), exhibited high thermal stabilities and were liquid crystalline at room temperature.